Things That Can Distort Your Blood Pressure Results

Your blood pressure is a measurement of the pressure your circulating blood is putting on the walls of your arteries, and it’s expressed as two numbers: (1) systolic pressure (top number) is the force exerted on your arteries as your heart beats, and (2) diastolic pressure (bottom number) is the force exerted when your heart rests between those beats. Normal blood pressure is considered to be less than 120 systolic and 80 diastolic (120/80). Anything higher is considered high blood pressure (hypertension), while anything under 90/60 is considered low blood pressure (hypotension). There are several factors that can affect your blood pressure reading and here are the top three. 
White Coat Syndrome — White Coat Syndrome is the anxiety that some people feel when in a doctor’s office. According to the AMA, this can result in a reading error of up to 26 mm Hg (millimeters of mercury), which can easily push your reading into the high blood pressure range temporarily. Patients with WCS are often asked to arrive early for appointments to have some time to relax before being examined. 

The Mechanics — The physical arrangement when you have your blood pressure taken can have a big impact on your numbers. 
  • Back Support: Sitting in a chair that supports your back will reduce errors. Having an unsupported back can add as much as 10 mm HG to your reading. 
  • Arm Support: If you hold your arm lower than your heart, your reading can be off by as much as 23 mm HG. It’s best to support the arm so you can keep it at the right elevation easily. Simply resting your arms on the arms of the chair will accomplish that.
  • Legs and Feet: Sitting with your legs crossed can add up to 10 mm HG to your reading, and not supporting your feet can add another 10 mm HG. Sit with your legs uncrossed and your feet flat on the floor. 
  • Bare Arm: Taking your blood pressure with the cuff around one or more layers of clothing can add up to 40 mm Hg. 
  • Cuff Size: Finally, the cuff of the blood pressure machine must be the right size. Studies have shown that heavier people often get inaccurately higher readings because the standard-size cuff is too small and constricts their arm too much. 
Behavior — Even if your body is physically arranged properly for the reading and you don’t suffer from White Coat Syndrome, other behaviors can affect your reading. 
  • Talking: Having a conversation while having your blood pressure taken can increase your numbers by as much as 15 mm Hg. 
  • Full Bladder: If you’re getting your blood pressure taken, go to the bathroom first. A full bladder can add up to 33 mm Hg. 
  • Food and Drugs: It’s not surprising that eating a big meal or ingesting things like alcohol, nicotine, and caffeine before your test can distort the readings. You should avoid taking in food or substances for a while before your test.